Enhancing bioaccessibility of isoflavone aglycones in fermented soymilk: Effects of different lactic acid bacterial strains and thermal treatments

Abstract

This study evaluated the combined effects of three lactic acid bacterial strains and different thermal processing conditions (boiling at 100 °C for 15 min or autoclaving at 121 °C for 15 min) on the bioaccessibility of isoflavone aglycones and other forms in soymilk and fermented soymilk using an in vitro gastrointestinal digestion model. Autoclave treatment promoted the conversion of malonyl isoflavones to their glucoside forms, resulting in a higher glucoside content in autoclaved soymilk. Because Lactiplantibacillus plantarum TIG-0010 exhibited the highest β-glucosidase activity, soymilk that was autoclaved and fermented with this strain showed a significantly higher aglycone content (292.6 nmol/g) than autoclaved soymilk (48.8 nmol/g) without fermentation. Gastrointestinal digestion results revealed lower digested amounts and bioaccessibility of aglycones than glucosides. Furthermore, two autoclave cycles (15 min at 121 °C per cycle) applied to soymilk fermented with L. plantarum TIG-0010 further enhanced both the digested amount and bioaccessibility of aglycone isoflavones.